The ‘core’ or 'pit' of the primary stage of advanced implosion-type fission weapons

Just oddly curious about this. Of course there have been many developments in firing circuitry, explosive lense geometry, explosives and detonators and initiators (and so on) but what of the core itself? Public domain material indicates that the core of early implosion weapons (i.e. gadget/fatman, joe 1) was spherical, and that soon after, levitated pits (i.e. with an air gap around the core) were introduced. Other developments such as the implementation of composite (i.e. Pu and HEU cores) soon ensued, as did boosting to provide high energy fusion neutrons for more efficient fission. But how has the actual shape of the core developed? There have been vague references to developments such as explosive lenses being used to ‘fire’ separate pieces of fissile material together which is further compressed. Also, public source material indicates that small devices (such as those used in small recoilless –rifles and artillery shells) may involve an ‘oblong’ shaped core with explosive charges positions mostly at each end. In the fictional ‘Sum of All Fears’ Tom Clancy (who certainly talks his fair share of crap) hints at a primary-stage core in a multistage device which resembles a glass tumbler with the edges ‘bent’ out back towards its base. Is anyone positioned to offer any insight on what the last 60-odd years have seen in regard to what is the best shape for fissile material that is intended to be compressed at the right speed and under the right conditions to allow the most efficient nuclear detonation?

In the fictional ‘Sum of All Fears’ Tom Clancy (who certainly talks his fair share of crap) hints at a primary-stage core in a multistage device which resembles a glass tumbler with the edges ‘bent’ out back towards its base.

Tangent: IIRC, in the afterword for that book, Clancy said he intentionally changed some of the details of the bomb fabrication. Kind of a gasoline-and-orange-juice thing.

And if I were trying to build one, I'd probably go with some sort of linear accelerator - a charge behind each piece of fissile material to drive 'em together, then a slightly delayed "sleeve" charge around the place where the pieces would collide (time the shockwave to just barely precede the collision). But maybe that's just The Way Things Work talking.

Unless you build the things, detail on Gen 3 nuclear weapons and up are not going to be easy for you to track down. Still classified and all that.

I've personally found the most information on forums for nuclear physicists. They talk about the theoretical science, but the real technical details are intentionally obscure. Still, you can garner a lot of hints about the capabilities of a 21st century nuclear arsenal from their chatter.

I had a friend back in high school who was basically not a very happy person and he told me that his dream in life was to be locked up by the government in Area 51 developing weapons of mass destruction. Then he sent me some kind of ASCII diagram of an atomic bomb. It was funny.

Well, these devices have an extremely significant social history, having shaped the balance of power in the modern world. I think it is fine to express some level of curiousity as to how they now 'tick'.

it would seem that open-source material such as globalsecurity.org suggests that advanced modern multistage devices such as the w-88 may feature a 'prolate' primary and spherical secondary, with this configuration having the advantage of reducing size.

First of all, although not a physicist, physics (especially fast-fission devices) are a backyard hobby of mine. The cost-efficient (best bang for your buck, so to speak) would be to use a fusion-boosting compound. However, since you stated that you wanted the optimal (which is again, a code-word for VERY EXPENSIVE) design, I'd recommend a perfect sphere. It's a simple notion that's proven to work without trying to get all fancy about it. Typically the further you gravitate from a perfect sphere, the increased chance you have of the material getting blown apart (a form of nuclear pre-detonation) instead of the material creating the desired thermonuclear reaction...it can be done, of course; however, your detonation sequence and layout become really, really, complex.

And for the love of 10 microwaved cats---why are you asking this here? I've already received three threatening phone calls from Homeland Security, and I haven't even finished typing this response.